Coupling Capacitor Question (Parallel caps)

[RichP4003]

I got some monoblock tube amplifiers recently, Luxman MB88u (KT88 push pull). I noticed a few oddities about the coupling caps (one has different values than the other, for example). I wanted to upgrade anyway, but had a question from something Ive noticed examining the amps and the schematic. The first coupling cap, according the other wiring diagram, is a 4.7u. However, on the amplifiers, there are 2 2.2u connected in parallel (they are board mounted and the board has a provision for 2).

Is there an advantage to this layout vs just getting a 4.7u and calling it a day (which would be a little cheaper)? Ive also noticed, based on other amplifiers like them that have sold (Hifido in Japan does an excellent job documenting all the stuff they have sold in the past) some only have one of the 2.2u caps in that position; the other is absent.

Thoughts?

 

[BinaryMike]

This reads like the engineers had some changes of mind over the course of production. The units with 2.2uF only might have other differences as well. Unless you're prepared to make a thorough investigation of subsonic frequency response and stability issues, I say it's best to stick with capacitor values very close to what's extant in your particular chassis.

 

[gadget73]

Electrically it comes out to 4.4uf, which is close enough to not matter. Possible it was just a space consideration. 4.7uf 250v film cap is not exactly dainty, and it would have been even bigger when these were made.

Also, honestly I doubt you'd ever measure much performance difference between any of those parts. I would probably just put it back how it was, though me being me I would not really be inclined to even change them unless they are bad.

 

[RichP4003]

Electrically it comes out to 4.4uf, which is close enough to not matter. Possible it was just a space consideration. 4.7uf 250v film cap is not exactly dainty, and it would have been even bigger when these were made.

Also, honestly I doubt you'd ever measure much performance difference between any of those parts. I would probably just put it back how it was, though me being me I would not really be inclined to even change them unless they are bad.

Thats a good point.. and yes, leaving well-enough alone would be the wise choice. I did want to replace the other ones (the 0.22u ones) because one of them was replaced with a 0.47 on one of the amplifiers. For my own audiophillia-nervousa, I need those to at least match!